A conventional ink jet printer is disclosed in, for example, Japanese Laid-open Patent Application No. 24001/1994 (Japanese Official Gazette, Tokukaihei No. 6-24001, publishing date: Feb. 1, 1994).
As shown in FIG. 41(a), an ink jet printer disclosed in the above publication is arranged in such a manner that an ink carriage 100 is supported by a screw shaft 101 provided in a direction that intersects at right angles with a direction in which a recording paper 102 is transported, and the ink carriage 100 is allowed to run linearly along the screw shaft 101.
In addition, as shown in FIG. 41(b), the ink carriage 100 has four ink tanks including a yellow ink tank 103a, a red ink tank 103b, a blue ink tank 103c, and a black ink tank 103d, each provided with their respective ink heads 104a, 104b, 104c, and 104d formed on the bottom surfaces facing the recording paper 102 downward.
Each of the ink heads 104a, 104b, 104c, and 104d is provided with a line of a plurality of ink nozzles 105 (eight in the drawing). Accordingly, a jet of ink is directed to the recording paper 102 simultaneously from each ink nozzle 105 in the line, so that print is made per line height, for example.
Thus, as shown in FIG. 42, print is made by running the ink carriage 100 linearly directing a jet of ink downward to the recording paper 102 while the recording paper 102 is transported in the transportation direction.
However, the foregoing conventional ink jet printer has a problem that it can not increase a printing rate, because the printing rate is determined by a distance a recording paper has to travel in the printer, that is, the length of each line of the ink nozzles 105 and a running rate of the ink carriage 100.
The conventional ink jet printer has another problem that it can neither print out an overstrike character nor perform a double-side printing, and that it can not perform high-speed printing such that meets a user's demand when making print of high resolution or mixed information including, for example, a watermark and print data.